ρ0 Photoproduction In Auau Collisions At √s Nn=62.4 Gev Measured With The Star Detector

摘要

Vector mesons may be photoproduced in relativistic heavy-ion collisions when a virtual photon emitted by one nucleus scatters from the other nucleus, emerging as a vector meson. The STAR Collaboration has previously presented measurements of coherent ρ0 photoproduction at center of mass energies of 130 GeV and 200 GeV in AuAu collisions. Here, we present a measurement of the cross section at 62.4 GeV; we find that the cross section for coherent ρ0 photoproduction with nuclear breakup is 10.5±1.5±1.6 mb at 62.4 GeV. The cross-section ratio between 200 GeV and 62.4 GeV is 4.4±0.6, less than is predicted by most theoretical models. It is, however, proportionally much larger than the previously observed 15%±55% increase between 130 GeV and 200 GeV. © 2012 American Physical Society.